Metallic skin-covered structure



Aug. 14, 1945. 1 WATTER 2,382,357

METALLIC SKIN COVERED STRUCTURE Filed March 6, 1943 5 Sheets-Sheet 1 INVENTOR Mic hael Waiter A TTORNEY Aug, 14, 1945. I M, WATTER 2,382,357

" METALLIC SKIN COVERED STRUCTURE Filed March 6, 194:5 5 Shets-Shget 2 INVEN TOR ATTORNEY Aug. 14, 1945-. wATTER 2,382,357

METALLIC SKIN COVERED STRUCTURE Filed March 6, 1943 5 Sheets-Sheet 3 INVENTOR Mighagl Watt'er. I

A TTORNE Y Aug. 14, 1945.

M. WATTER METALLIC S'KIN COVERED STRUCTURE Filed March 6, 1943 5 Sheets-Sheet 4 INVENTOR Michael Wgfiter.

ATTORNEY Aug. 14, 1945. M. WATTER 2,382,357

METALLIC SKIN COVERED STRUCTURE Filed March e, 1945 V 5 Sheets-Sheet 5 I I Mihael Whiter.

"L"/( I m IN VENT OR ATTORNEY Patented Aug '14, 1945 g METALLIC SKIN-COVERED STRUCTURE Michael Watter, Philadelphia, Pa, assignor to Edward -G. Budd Manufacturing Company, Philadelphia, Pa., a corporation of Pennsylvania Application March 6, 1943, Serial No. 478,231

8 Claims. (01. 189-34) This invention relates generally to metallic structures such as are adapted for use in the construction of vehicles of various types including, for example, airplanes, railroad cars, automobiles, ships and like products of manufacture where a metallic surface or "skin is mounted upon an inner, supporting, load-resisting or loadtransmitting frame to form an integral part of the completed vehicle. One example of such a structure is found in an air reaction surface of.

an air transport vehicle, such as an airplane wing, a stabilizer, fin, or similar part, and for the purposes of the present disclosure the invention will be described in connection with such a member.' Nevertheless, it will be apparent that the invention hereinafter disclosed embodies features which are equally well adapted for use in other functional capacities and in other forms of vehicles.

An object of this invention is to provide an integrated metallic structure of the type specified formed substantially entirely of metallic members joined together by welded joints, the construction and arrangement being such as to provide not only ready access to the parts for welding during manufacture and assembly, but also a finished product combining great" strength with lightness of weight.

A further object is to provide an improved construction of reinforced skin blanket for metallic structures such, for example, as airfoils and the like.

A further object is to provide an airfoil structure designed not only to embody a lightweight skin blanket of great strength, but one which can be easily and rapidly assembled with the supporting framework by welding easily accessible par-ts.

A still further object is to provide a metallic structure such, for example, as an airfoil of the Fig. 3 is a sectional view on the line 3-3 of Fig. 1;

Fig. 4 is a view showing the manner of assembling the parts forming the center panel of Fig. 3;

Figs. 5 and 6 are vertical sections on the lines 5 5 and 6-6, respectively, of Fig. 2;

Fig. 7 is a partial perspective view showing a reinforced skin blanket mounted on a portion of the supporting framework; and

Figs. 8, 9, 10 and 11 are reduced scale, somewhat diagrammatic-views showing the successive steps in assembling a metallic structure such as the airfoil shown in Figs. 1 to '7.

In the illustrated embodiment of this invention a supporting framework is formed of longitudinally extending spars and transverse spar-connecting ribs. A stressed metallic skin blanket is I provided with a plurality of reinforcing members stressed skin type. constructed and arranged to have a skin blanket of great load carrying capacity.

in the form of stringers of suitable cross section which are secured in spaced parallel positions to the inner face of the skin blanket, as by welding. The stringers are of such length as to extend across the surface of the skin blanket between the spars to which the blanket is directly secured as by welding. The strength of the skin blanket is additionally increased by longitudinally extending stiffeners of suitable cross section which are secured to and extend transversely across the stringers between the successive ribs of the supporting framework. Preferably the stifleners are welded to the stringers. The adjacent ends of successive stiffeners on opposite sides of the ribs are connected by saddle members or the like which extend across and are secured to the ribs and are connected at each end to the adjacent stiffener members. The arrangement is such that the reinforced skin blanket can Ice-formed as a unitary sub-assembly.

As illustrated, the present invention is shown in connection with an airfoil in the form of a vertical fln' 2| having a rudder 22 hinged to the fin in any suitable manner. The structure com- These and other objects which will be apparent I to those skilled in the art are accomplished by the present invention one embodiment which is illustrated in the accompanying drawings, in

I which:

Fig. l is a side elevation of av metallic structure constructed in accordance with one embodiment of this invention, showing the same embodied in an airplane fin as an example of structures to which the invention is adapted;

Fig. 2 is a, similar view on an enlarged scale of the center panel of the airfoil shown in Fig. 1;

prises an inner, supporting framework and a stressed, reinforced skin blanket secured thereto. The inner framework is formed by a plurality of parallel, longitudinally extending spars 23 connected together by transversely extending ribs 24, together with several hinge ribs 25 which are of heavier construction than the remaining ribs 24, being called upon to support the rudder hinge frames 26 as generally indicated in Fig. 1.

Each spar 23 comprises chord members 21, of flanged channel or hat-shaped cross section connected by struts 28 at the point of intersection with the ribs 24. At one end, the strut 28 is assess? extending flanges 41 in a manner similar to the chords 8! of the typical ribs 28. 4

A reinforced skin blanket 88 is secured across the spars and ribs to form a surface such, for example, as the airfoil surface illustrated. The

, skin blanket of sheet metal such as stainless steel back of gusset plates 88 which arealso welded to the side walls of the adjacent chord member 21. Each chord member 21 has longitudinally extending reinforcing grooves 88', one in the web and one. in each side wall, and the gusset plates are welded to the side walls at each side of such groove. Each spar also includes diagonal struts .38 welded at one end to a connecting plate 88 which is in'tum welded to gussets 8|, see Figs. and 7, andat opposite endsis welded to a connecting plate 81 which is in turn welded to a gusset 38 secured to achord of one spar 21.

Where the struts 28 are located, adjacent spars are connected by transverse ribs 28, as shown in Figs. 3, 4 and 'l.' Each rib 24 includes chord members ll ,of any suitable section, shown as of Z-shape. Thechords ll of each such rib are connected by transverse struts l2 welded to gusset plates 83 which are in turn welded to the adjacent chord 4|. 'A diagonal strirt 48 is connected to the diagonally opposite triangular gussets l8, and

'a pair of short diagonal struts 48 are provided at each end of the rib for connection to a gusset 46 mounted on the adjacent spar strut 28 intermediate the ends thereof. The reverse flange of each hat-shaped spar chord 21 is cut away at 21a, see Fig. 7-, to accommodate the ends of the rib chord members 4| and the latter are welded tothe outwardly extending flanges 41 of the spar chord 21.

As above pointed out, hinge ribs 28 are provided in place of the usual ribs 28 at certain predetermined positions, the hinge ribs being of stronger construction to resist the stresses imposed on them by the hinge frames 28 which are connected thereto for hingedly supporting the rudder 22, see Fig. 1. As shownin Figs. 5 and '1, each hinge rib includes chord members 81 which are preferably of flanged channel or hat-shaped cross section. The chords are connected by transverse struts 52, each strut being formed by a pair of flanged channel or hat-shaped sections 88, see Fig. 6, having their flanges welded together to form a unitary hollow strut. gusset plates '84 being welded to the opposite sides of each sections welded together, connected at one end to a chord member 8| through the gussetplates 84, and at their other ends connected to a flat gusset plate 81 positioned between the hat-shaped sections. The gusset 81 at each end of each hinge rib is mounted on a spar strut 88 formed by a pairof hat-shaped sections 88'positioned back to back and connected at one end to the gusset plates 88 on the adjacent spar chord 21 and at the other end to gusset plates 8| connected to the opposite spar chord 21. The reverse flanges of the hat-shaped spar chords are also cut away as at 21a to accommodate the ends of the hinge rib chords 81 which are welded to the outwardly is spot welded at each edge to the flanges 41 of the spar chords 21. As illustrated in Figs. 3 and '1, the skin blanket is welded at one edge to the near flange 81 of the spar chord so as to leave the chord panel open. 'At the other edge, the skin blanket is welded to the near flange 41 but extends across the channel of the chord and across the opposite flange 81, forming therewith a slot for receiving the edge of an adjacent section of skin blanket, or other element, to which it and the adjacent flange 81 can both be welded to form a unitary structure.

The. skin blanket is provided with a plurality of transversely extending parallel stringers 85, also shown as hat-shaped, which are welded through their bottoms to the inner face of the skin sheet 88 and extend across the skin sheet between adjacent spar chords 21, the lengths of the stringers 88 being such that space is left on the skin blanket for direct engagement with and welding to the flanges 81 of the chord members 21. The stringers can be applied and secured to the skin sheet prior to the application of the latter to the spars. In addition to the stringers 85, the skin blanket is preferably reinforced by longitudinally extending stiifeners 88 which extend across the stringers 85 parallel to the blanket II and 55, at that side of the ribs 24 and 25. The

length of each stiflener is such as to leave space to receive the rib chords if and 8| therebetween so that the skin blanket 88 can be attached directly to these chord members. Saddles or cross-overs 81 of hat-shaped cross section, see Figs. 3, 6 and '7, are spot welded through their flanges to the flanges of the adjacent ends of successive stiffeners 88 and extend across and are spot'welded to the rib chords Ill and 6!. eflect, this forms a continuous stiffener from one end of the structure to the other.

It will be apparent that' the skin blanket can have the stringers 68 and the longitudinal stiffenera 88 welded in place thereon before the skin blanket is applied to the supporting framework comprising the spars 28 and transverse .ribs 28 and 28, thus providing a sub-assembly consisting of the reinforced skin blanket with spaces formed between the reinforcements to receive the chord members of the various spars and ribs to all of which the blanket is directly secured.

The successive, steps followed in assembling a metallic structure embodying the present invention are indicated diagrammatically in Figs. 8 to 11. A-spar comprising the chords'21, connecting struts and the like is positioned as shown in Fig. 8.. The various ribs including both typic ribs "and binge ribs 28 are secured at properl spaced intervals along the spar by welding their chord members to the flanges 81 of the chord members and by welding the end diagonals 48 and 88, as the case may be, to the gusset plates l8 or 81. This provides the partial assembly illus- 78 trated in part in Fig. 9.

86 are then welded across the stringers. The

stringers and stiffeners are so arranged as to" leave the necessary spaces for the skin sheet tobe subsequently welded to the chord members of both the spars and the ribs. Each skin blanket sub-assembly is then placed in position with the chords of the spars and the chords of the ribs located in the spaces provided therefor at the ends of the stringers 65 and between the ends of successive longitudinal stifl'eners 86. As shown, the skin blanket is positioned to leave open the channel of the chord section of this spar, the. edge of the blanket being welded to the near flange thereof. Thereafter, the saddles 61 are welded to the stifieners 68 and to the rib chords. Then, the next spar 23 is placed in position, as shown. in Fig, 11, the near flange 41 of the chord member being welded to the skin sheet which extends across the channel of the chord section to form the slot 84 as above described.

It will be apparent that the stressed skin blanket, being directly mounted on and welded to all members of the inner framework, both longitudinal spars and transverse ribs, and being reinforced by transverse stringers secured to the inner face of the skin sheet, and being further reinforced by the longitudinal stiifeners extending across and welded to the stringers, which stiffeners are connected at the ends to each other and to the rib chords by the saddles 61, provides a metallic structure of great strength, despite a relatively light weight, in which the skin bianket itself is capable of withstanding relatively heavy loads and forms, in fact, an integral part of the completed structure.

The invention has been described only in connection with the central portion of the fin illustratedi, that is, the portion disposed between can be variously modified and adapted within the scope of the appended claims. What is claimed is: 1. A metallic stressed skin structure comprising a thin sheet metal skin having at one side thereof a plurality of spaced, generally parallel, reinforcing stringers, a plurality of skin-supporting ribs having chords adjacent said skin at said one side, said ribs being generally parallel to said stringers and there being a plurality of said stringers at each side of at least one of said rim, stringer bridging stiffener members disposed the two spars 23. The same construction is also applicable to that portion of the structure lying at the left of the left spar 23 as viewed in Figure l. The invention is also applicable to mono-spar and other constructions employing a plurality of spaced ribs, it being primarily directed to the relation of the reinforced skin blanket'to the ribs. The stifl'eners 81 provide an efficient and extremely effective means for not only the transfer of stresses between the ribs and the portions of the skin blanket intermediate adjacent ribs, but also for assisting the stringers 66 in maintaining the airfoil contour and for minimizing drumming or vibration of such inter mediate blanket portions- Although, for the purposes of the present disclosure, the invention has been described in connection with the center panel of an airplane fin, it will be apparent that the novel features herein disclosed are equally well adaptedto metallic structures having other functions, other configurations, and employed for other purposes. It will also be apparent that the other panels of the illustrated fin, embody the same novel features as the center panel described. Also, that the specific details of the supporting framework are subject toconsiderable variation. Obviously the invention is neither limited to the particular article nor the'details described. but

above and crosswise of and secured to the tops of said stringers intermediate the ends thereof, there being at least one such bridging member between adjacent ribs, and terminating adjacent said adjacent ribs, said bridging stiffener mem. bers and said rib chords having walls disposed approximately in a common plane parallel to the skin, and means rigidly securing the top of each end of the bridging member to the top of a chord of the adjacent rib;

2. A metallic stressed skin structure comprising a thin sheet metal skin having at one side thereof a plurality of spaced, generally parallel reinforcing stringers, a plurality of skin-supporting ribs having chords adjacent said skin at said one side, said ribs being generally parallel to said stringers and there being a plurality of said' to the bridged stringers, each end of a stiffener terminating adjacent a rib, there being at least one stiffener at one side of one rib substantially aligned with a stiffener at the other side of said one rib, said bridging stiffener members and said rib chords having walls disposed approximately in a common plane parallel to the skin, and rigid means extending through the one rib above a chord thereof rigidly connected with the tops of the adjacent ends of said aligned stringers.

3. A metallic stressed skin structure comprising a thin sheet metal skin having at one side thereof a plurality of spaced, generally parallel, reinforcing stringers, a plurality of skin-supporting ribs having chords adjacent said skin at said one side, said ribs being generally parallel to said stringers and there being a plurality of said stringers at each side of at least one of said ribs, stringer bridging stiffener members extending above and crosswise of the tops of said stringers between adjacent ribs and being rigidly secured to the tops of the bridged stringers, each end of a stiffener. terminating adjacent a rib, there being at least one stiffener at one side of one rib substantially aligned'with a stiffener at the other side of said one'rib'las'aid bridging stiffener members and said rib chords having walls disposed approximately in acommon plane parallel to the skin, and rigid means extending through the one rib above a chord thereof rigidly connected with the tops of the adjacent ends of said aligned stiffenersj and to the top of the chord of said one rib.

- 4. In a metallic skin covered structure having spaced truss-type rib elements and a thin gauge sheet metal skin spanning said rib elements and secured to the chord members of the rib elements at one side of the structure, the combination with said skin and rib elements of a group of spaced skin-reinforcing stringers parallel to said rib elements and secured to said skin between adjacent rib elements, a stringer reinforcing stiffener channel formation and having opposed side cured through their bottoms to the skin reinforcing stringers, and said saddle members being oi flanges abutting and secured to the corresponding side flanges of said stiifeners and to said rib chord member.

'1. In a metallic skin covered structure havin spaced truss-type rib elements and a thin gauge their bottoms to the skin-reinforcing stringers,

and said saddle members being-secured to said side flanges.

5. In a metallic skin covered structure having spaced truss-type rib elements and a thin gauge sheet metal skin spanning said rib elements andsecured to the chord members of the rib elements at one side of the structure, the combination with said skin and rib elements of a group of spaced skin-reinforcing stringers parallel to said rib elements and secured to said skin between adjacent rib elements, a stringer reinforcing stiflener bridging and secured to the stringers or each oup and terminating at its ends adjacent the chord members of adjacent rib elements, and a rigid saddle member interconnecting and securing the stifiener of one stringer group at one side of one rib element with the stifl'ener of the stringer group at the other side of said one rib element, said saddle member extending transversely through therib element adjacent the chord member thereof'to which the skin is secured, said stifleners being of channel formation and having opposed side flanges and being secured through their bottoms to the skin reinforcing stringers,-

and said saddle members being of channel formation and having opposed side flanges abuttin and secured to the corresponding side flanges of said stifleners.

6. In a metallic skin covered structure havin spaced truss-typed rib elements and a thin gauze sheet metal skin spanning said rib elements and secured to the chord members 01 the rib elements at one side of the structure, the combination with aid skin and rib elements of a group of spaced skin-reinforcing stringers parallel to said rib elements and secured to said skin between adjacent rib elements, a stringer reinforcing stiflener bridging and secured to the stringers of each roup and terminating at its ends adjacent the chord members of adjacent rib elements, and a rigid saddle member interconnecting and securing the stiffener-oi one stringer group at one side of one rib element with the stiflener of the stringer group at the other side of said one rib element, said saddle member extending transversely through the rib element adjacent the sheet metal skin spanning said rib elements and secured to the chord members of the rib elements at one side of the structure, the combination with said skin and rib elements of a group of spaced skin-reinforcing stringers parallel to said ri-b elements and secured to said skin between adjacent rib elements, a stringer reinforcing stiflener bridging and secured to the stringers of each group and terminating at its ends adjacent the chord members of adjacent rib elements. and a rigid saddle member interconnecting and securing the stiflener of one stringer group at one side of one rib element with the stifiener of the stringer group at the other side of said one ri-b element, said saddle member extending transversely through the rib element adjacent the chord member thereot to which the skin is secured, said stringers, stifieners and saddle members each being of channel formation having opposed side flanges, said stringers being secured through their channel bottoms to said skin, said stiifeners being secured through their bottoms to the side flanges of said stringers, and said saddle members being secured through their side flanges to the side flanges of said stifleners.

8. In a metallic skin covered structure having spaced truss-type rib elements and a thin gauge sheet metal skin spanning said rib elements and secured to the chord members or the rib elements at one side of the structure, the combination with said skin and rib elements of; a group of spaced 0 skin-reinforcing stringers parallel to said rib elechord member thereof to which the skin is secured, said stifleners being of channel formation and having opposed side flanges and being sements and secured to said skin between adjacent rib elements. a stringer reinforcing stiffener bridgin and secured to the stringers of each group and ter'minatingat its ends adjacent the chord members of adjacent rib elements, and a rigid saddle member interconnecting and securing the stiffener of one stringer group at one side of one rib element with the stifiener of the stringer gi'oup at the other side oi said one rib element, said saddle member extending transversely through the rib element adjacent the chord member thereof to which the skin is secured, said stringers, stifleners and saddle members each beingot channel formation having opposed side flanges, said stringers being secured through their channel bottoms to said skin, said stiflenersbeing secured through their bottoms to the side flanges of said stringers, and said saddle members being secured through their side flanges t0 the side flanges of said stifleners and through their side flanges to said rib chord member.

MICHAEL-WATI'ER. 

